Conventional universal type series (or compound) motors are used in driving various kinds of industrial machinery and, particularly, electrical tools or small household appliances. However, series motors have the undesirable characteristic of being very load sensitive. As the load on the motor is decreased, the speed of the motor will increase causing excessive noise and excessive wear and tear on drive elements such as gears and bearings. In view of such defects, it is advantageous to limit the speed of series or compound motors.